CNES, ASI Favor Solid-Rocket Design For Ariane 6

If things had gone according to plan, Europe would be flying a more powerful and efficient version of its Ariane 5 rocket today, one that could compete in the commercial market without public subsidies, and development of a next-generation launcher would be well underway.

Instead, the Ariane 5 suffered a serious failure in 2002 that slowed plans to boost its performance and shelved what were mostly French ambitions to start work on a less costly successor.

An evolution of the Ariane 5 ECA that now delivers roughly half of the world's communication satellites to orbit each year, the enhanced Ariane 5 ECB would have entered service in 2006. But it was 2008 before the European Space Agency (ESA) approved low-level funding for early development. The project was rebranded the Ariane 5 Midlife Evolution (Ariane 5 ME), and the money—roughly €300 million—started to flow, most of it going to Ariane 5 prime contractor Astrium Space Transportation's facility in Bremen, Germany.

As ESA's largest contributor, Berlin is eager to see additional funding approved for Ariane 5 ME when ministers from the agency's 20 member states meet next month to hash out a multiyear spending plan. Few question Germany's influence over the space agency, or the likelihood that Ariane 5ME will survive the November budget meeting. But last month ESA Director General Jean-Jacques Dordain said he favors starting work now on a next-generation rocket.

“I strongly believe we have to decide, as quickly as possible, to develop a new-generation launcher to be competitive in the market as it is forecast, and with the competitors,” Dordain said at the Berlin air show last month, a reference to new launch vehicle developments in India, China and the U.S., where Space Exploration Technologies' low-cost Falcon 9 is challenging the global launcher market (see page 30).

Aware of looming competition, French space agency CNES has been studying next-generation launch vehicle concepts for a modular Ariane 6 that would use existing technologies and production facilities to replace the cumbersome, costly and commercially reliant Ariane 5.

The timing, observers say, could be critical, as Europe has not faced such a momentous decision on a major launch vehicle development for nearly 25 years. During that time, France has been the primary financier of launch vehicle development in Europe. But for the first time in ESA's nearly 40-year history, the German government has formed a consensus in support of maintaining Europe's independent access to space and says it will contribute one-third of the cost to fund launchers, if ESA will approve €1.4 billion ($1.8 billion) for full-scale development of the Ariane 5ME.

Astrium says the money could yield an operational upgrade by 2017, freeing ESA member states from €120 million in annual price supports paid to Arianespace, the European launch consortium that manages commercial Ariane 5 missions. Such relief, however, would come more than a decade after the Ariane 5 ECB was slated to enter service, a piece of history not lost on the French, who are eager to start work on what they have tentatively dubbed Ariane 6.

“What has bothered Germany is that its position on Ariane 5 ME is viewed as childish thinking focused on industrial policy,” says Marco Fuchs, CEO of German satellite manufacturer OHB. Industry has been arguing for a decade for launchers to be of strategic import to Berlin, he says. “If France wants Ariane 6, they have to go through Ariane 5 ME,” Fuchs asserts.

Christophe Bonnal, a CNES technical specialist, says three modular design options are in the offing: two solid-propellant rockets and an all-liquid-fueled launcher with solid strap-on boosters.

To date, the CNES analysis favors the solid-rocket concepts. Bonnal says even in the worst-case scenarios that assume a 20% decline in market price after 2020, when the rocket would enter service, the solid-rocket configurations could survive on eight launches per year, including three institutional ones for government customers.

“Definitely, we prefer the solid configuration today,” Bonnal said Oct. 3, during the 63rd International Astronautical Congress (IAC) in Naples, Italy.

Bonnal says each design would be capable of delivering at least 2,100 kg (4,629 lb.) to geostationary transfer orbit (GTO), the destination of most commercial telecom satellites, and that two of them—one solid, one liquid—could haul more than 8,000 kg to GTO.

The three concepts have several features in common: a cryogenic upper stage 4.4 meters (14.4 ft.) in diameter with a common bulkhead architecture propelled by the Vinci engine that is in development under Ariane 5ME; a large fairing 5.2 meters in diameter; and a payload interface of 1,780 mm (70 in.) with the payload encapsulated.

One solid-motor configuration, the P1B, is based on a monolithic composite first stage with a 3.7-meter diameter powered by a P180 engine. A second stage would use a P110 engine topped with the cryogenic 31-ton upper stage and up to six optional P39 strap-on boosters.

Bonnal says launcher control would be achieved without thrust-vector control (TVC) for the strap-ons, but empennages are being considered to limit the dynamic nozzle deflection angle. “If we start having a thrust-vector control on all of the boosters, then in terms of cost, we're lost,” says Bonnal.

For the P1B, the first set of P39 boosters would be ignited at lift-off and then jettisoned, while the second set, depending on the configuration, could be ignited in flight and not jettisoned.

Bonnal says CNES is preparing wind-tunnel tests to adjust the margin policy, and pressure oscillation has been assessed for different flight phases.

Similar to the P1B, the all-liquid H2C would use up to six strap-on boosters to carry as much as 8,400 kg to GTO. Twin main engines, capable of 150 tons of vacuum thrust derived from the Ariane 5's Snecma-built Vulcain 2, would comprise the H165 first stage, which would be topped by a 31-ton cryogenic upper stage, he says.

A third design, the P7C, would use a single solid-rocket stage based on the P135 engine as a building block to be arranged in linear and “faggot” configurations. Like the P1B, the P7C would use a 3.7-meter-dia. monolithic casing. But, unlike the P1B, each of the P7C stages would feature TVC, a factor that could increase costs.

“You could have a configuration with three P135s making a real first stage, ignited all together on the ground and separated all together, so there is no need to have separations between the stages,” Bonnal says.

The P7C has the advantage of smaller stages, with the P135 falling in the range of what Europe's mostly Italian-built Vega launcher demonstrated this year with its P80 first-stage engine, Bonnal says.

Indeed, Italy is eager for ESA to approve early work on such an Ariane 6 design, which could facilitate new development of a more powerful Vega engine that could lower production costs and greatly improve its competitiveness in the commercial smallsat market.

“For Vega, we want a P120 at a minimum,” says Enrico Saggese, head of Italian space agency ASI.

Saggese says moving to the more robust P135 could be a greater challenge, requiring a larger diameter for the stage, a new payload adapter and changes to existing tooling and production processes.

“But if we have a P135 for the Ariane 6, this could be worked,” he said on the IAC sidelines. “We are pushing for a design decision in Caserta,” a Naples suburb where the November ministerial will take place. c

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